Using agent-based modelling to plan for water supply and waste water infrastructure

Greater Accra Metropolitan Area, Ghana

The challenge to people and the environment

Our survival depends on having access to clean water. But in some city regions such as Accra, Ghana, poor city infrastructure leads to serious issues with water and sanitation.

This leads to significant impacts, for instance exposure to contaminated waste and flooding can lead to sickness and social upheaval caused by populations moving away from the affected region.

Identifying a solution: effective solutions for inclusive urban development

Accra’s ongoing water and sanitation challenges provide an excellent context to demonstrate effective solutions for inclusive urban development while maximising value for money and providing a foundation for broader urban transformation.

The pilot’s objectives: fostering multi-sector partnership to tackle major resilience challenges

Co-creating an innovative city-region integrated systems planning tool of to help tackle major resilience challenges.

This pilot was part of the Future Cities Africa Programme – 2014/16, to help cities to take an integrated approach to managing the risks and development needs they face.

GAMA was one of eight cities chosen in four African countries (Ghana, Ethiopia, Mozambique and Uganda). Stakeholders identified that water and sanitation was the biggest resilience challenge facing GAMA at the time.

The rewards: a suitable modelling environment to run scenarios, ask questions about, and design potential solutions to the GAMA’s regional WASH challenges.

The prototype is part of a multi stage development trajectory with three phases, after which the model will be released, as free to use.

  • Phase 1: Prototype development
  • Phase 2: Scale model logic to a full economy, covering all sectors 
  • Phase 3: Testing and validation in multiple country locations

The approach

Our first step was to ensure the single sector model prototype was fit for purpose and deemed useful and relevant to local stakeholders.

To this end, we delivered a series of activities, designed to boost local stakeholders’ integrated systems knowledge and build civic capacity, including:

  • An inaugural workshop to engage across sectors and assesses stakeholder needs.
  • Convening an expert technical working group (the “collaborator”), who led a learning journey in integrated systems planning and decision-making. The focus of this cross-sector team was on designing systems-level solutions to water and sanitation challenges in GAMA.
Tools and techniques used

We provided a suitable modelling environment for the team to run scenarios, ask questions about, and design potential solutions to the key regional WASH challenges.

The prototype is driven by data and assumptions on population, behaviours, service provision, risk and economics and run scenarios for between one and 20 year projections.

An iterative, collaborative process led to three case studies being rigorously tested to understand, at a systems level, how best to achieve sustainable water and sanitation developments in the GAMA.

Results calculations and assumptions for, policy briefings and private sector perspectives on the applicability of the based on three modelling scenarios:

  • Scenario 1 – Envisioning outcomes of ongoing WASH projects and steps to meet macro-level WASH targets including analysis of existing and proposed investments.
  • Scenario 2 – Examine the possibilities and costs of increasing household access to improved potable water to achieve SDG 6: 100% access to clean water.
  • Scenario 3 – Increase availability of clean, accessible, and affordable toilet infrastructure.

The following datasets were collected to describe the social, physical and economic interactions for the Water and Sanitation system in GAMA and are available on the open Africa data platform, including:

  • sociodemographic
  • behaviour
  • existing service infrastructure
  • locations and access to infrastructure
  • water and energy used (addressed through material and energy balance)
  • economic and environmental costs (capital/operational expenditures and revenues and GHG emissions)
  • new water, sanitation and energy technology performance
Modelling – use of

We codeveloped a comprehensive model of the WASH system in GAMA, based on the systems view below. This includes all the dynamics and interactions between the population, the physical infrastructure (including technologies) and resource flows (pipelines, water sources and waste-water treatment plants) and the economics.

Systems view of the Water and Sanitation challenges faced in GAMA.

Systems view of the Water and Sanitation challenges faced in GAMA.

Target user communities

Relevant ministries with jurisdiction over the provision of goods and services for citizens joined the Collaboratory to use as the repository from which to access planning and design relevant data and information.

The prototype collaborative working in Ghana elicited very positive and high-level advocacy and a strong demand to expand the prototype to cover all cities and regions in Ghana to support their 40-year development planning process with integrated and strategic planning tools.

Pilot results and next steps

A draft investment strategy was produced on how to achieve 100% access to water and sanitation, with the systems view favouring centralised water supply infrastructure and decentralised wastewater treatment and sanitation infrastructure.

Conclusions were made in accordance to the 3 scenarios:

Scenario 1
Centralised clean water supply is most efficient. A total investment of 1 billion USD is required to achieve this goal.
Although investing in the waste water system resulted in an increase in GHG emissions, when the project was beginning in 2010, water treatment levels were 0%. A cost-effective decentralised WASH system development would amount to 0.4 Billion USD total investment costs – due to the use of smaller-scale systems such as aerated lagoons and local activated sludge treatment.

Scenario 2
Discovered that a decentralised pipe provision scenario was less expensive, offering more jobs to local communities. Decentralised borehole technology requires maintenance of individual structures, with the opportunity for the creation of up to 4173 jobs by 2025.
The environmental impacts were radically decreased by having access to a local source of potable water. This is due to the reduction in greenhouse gases, and decreased sachet water use, predicted to create 153 tonnes of plastic waste per day in 2025.

Scenario 3
Decentralised toilet water treatment technologies such as aerated lagoon treatment plants and faecal sludge polymer separation drying plants are successful in achieving the 100% waste-water target.
Decentralised toilet systems are significantly less expensive, costing 0.41 billion USD over a 20-year period from 2010-2030, compared to the private toilet sector, which would cost over 2.98 billion USD in the same time-frame.
Decentralised public-sector toilets also offer the opportunity for creating up to 270 million USD collected as revenue in the 20-year time frame. An estimated 1753 jobs could also be created through the decentralised treatment model.

This strategy was presented to and welcomed by the Ministry of Finance, who wish to extend the work to all districts in Ghana, to harness systems level solutions to achieve major savings on infrastructure costs whilst achieving Ghana’s sustainable development objectives.

The project established a strong network of over 400 individuals from government, private academic and community sectors, which was built through in-country and remote support.

Contact us about this project

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More information on this work is included in the project report – PDF

A list of published journal articles concerning this project can be found on the – website